This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A tendon is a band of fibrous connective tissue that connects muscle to bone and is built to withstand tension. The tendon joins to a muscle at the origin of the tendon. There, collagen fibers from the muscle are continuous with those of the tendon. The tendon inserts into a bone at an enthesis where the collagen fibers are mineralized and integrated into the bone tissue. Tendons transfer the contractions of muscles and can exert an elastic force if stretched.
The Achilles tendon (also known as the calcaneal tendon) is a tendon of the posterior leg. It serves to attach the calf muscles (lateral and medial gastrocnemius muscle and soleus muscle) and the plantaris muscle to the heel bone (calcaneus).
The rotator cuff includes a group of tendons (supraspinatus, infraspinatus, teres minor, and subscapularis). This group of tendons and muscles in the rotator cuff connect the humerus (arm) with the scapula (shoulder blade).
Injury to a tendon can occur when the tensile load applied to the tendon exceeds its loadbearing capacity, causing the tendon to rupture. For example, rupture of the Achilles tendon is an injury that commonly occurs in males during sporting activities, generally as an acceleration injury (e.g., pushing off or jumping up). The diagnosis of an acute Achilles tendon rupture is usually straightforward. There is typically a snapping sensation and/or an audible snap in the posterior aspect of the ankle. The subject feels pain and is unable to bear weight due to both pain and weakness.
Treatment options for a ruptured tendon (such as a ruptured Achilles tendon or ruptured tendons in the rotator cuff) include conservative management, percutaneous repair, and open surgical repair. It is believed that open surgical repair provides the best chance for restoration of strength, power, and function of the muscle-tendon-bone complex with the lowest risk for repeat rupture. However, the management of a neglected Achilles tendon rupture poses certain problems to the surgeon as, by the time the subject is seen, the tendon ends have often retracted, forming a gap therebetween. Additionally, during surgery, the damaged tendon ends are debrided. Debridement may form a gap, and/or debridement may expand an already-existing gap. In order to treat the tendon to a full recovery, this gap must be closed. Various techniques have been used to eliminate this gap.
First, a surgeon can pull the two free tendon ends together and affix them to one another with sutures. However, when pulling the two free tendon ends together, each of the tendon ends is stretched. This weakens the tendon by decreasing the amount of tensile load the now-repaired tendon can withstand. This will cause functional deficiency of the tendon later, thereby increasing the likelihood of a repeat rupture.
Alternatively, portions of the Achilles tendon itself may be used to repair the tendon. For example, a strip of the superficial part of the tendinous portion of the proximal stump of the Achilles tendon may be used to augment repair. This is accomplished by making a posterior longitudinal incision and dissecting a half-inch by seven to nine-inch strip of tendon on a distal pedicle. The strip is then threaded through the trimmed ends of the ruptured tendon and sutured to them. However, this method also may not fully repair the tendon, as part of the tendon itself needs to be stripped away to repair the tendon.
Alternatively still, additional autologous tissue may be used to “bridge” the two tendon ends. For example, the tendon of the flexor hallucis longus (FHL) muscle of the leg has been used to bridge gaps in ruptured Achilles tendons. The FHL tendon is weaved through the ruptured Achilles tendon ends, and the distal end of the FHL tendon is adhered to the tendon of the flexor digitorum longus muscle of the second toe. Because the FHL tendon is a long tendon, it allows bridging of large Achilles tendon gaps. However, there are drawbacks to this treatment. For example, the process requires not only surgery to repair the ruptured Achilles tendon, but also to obtain the FHL tendon. Further, use of the FHL tendon impairs the normal function of the FHL tendon and FHL muscle. For example, in athletes, the loss of push-off from the toes (particularly the hallux) may cause difficulty when sprinting.
The tendon of the peroneus brevis muscle has also been used to bridge the gap of a ruptured Achilles tendon. The peroneus brevis tendon is harvested and passed through a transosseous drill hole formed in the heel bone. The peroneus brevis tendon is then passed back onto itself and sutured over the Achilles tendon. Like the use of the FHL tendon, above, use of the peroneus brevis tendon has drawbacks. For example, the normal function of the peroneus brevis tendon and peroneus brevis muscle is impaired.
Additionally, researchers have used human acellular dermal matrix grafts and porcine small intestinal submucosa for bridging tendon gaps in animals. However, these materials only provide a scaffold, but do not promote tendon cell growth and tissue repair to the degree of autologous tissue. Further, small intestinal submucosa can only withstand a small tensile load (approximately 40-50 N). This is much less than the tensile load capability of native tendon. This results in a weakened repaired tendon and the increased likelihood of repeat rupture.
In view of the drawbacks associated with current compositions and methods for tendon repair, a new and/or improved composition and method for repairing a ruptured tendon is desirable.